Displays are utilized in a wide variety of applications. One type of display is a projection display that employs a laser as a signal source. In instances in which the projection display is to be a color display, the projection display may include three lasers for providing signals having the three primary colors. These projection displays may also include a rotating mirror, such as a biaxial rotating mirror, in order to raster scan the signals provided by the lasers across a screen in a predefined manner. In relatively small projection displays, the rotating mirror may be a microelectromechanical system (MEMS) mirror that is configured to rotate along two axes so as to raster scan the signals provided by the lasers in order to create the desired image.
The lasers that may be employed by such projection systems may be relatively expensive and, as such, may undesirably increase the costs of the projection display. The lasers may also require a meaningful amount of power which may limit the operational life of a projection display, particularly in instances in which the projection display is power-constrained, such as in instances in which the projection display relies upon battery power. Because of the inherent inefficiency of the lasing process, lasers may also disadvantageously generate an appreciable amount of heat. If not properly managed, the heat generated by the lasers may create thermal distortion within the image and therefore adversely affect the color stabilization of the image.
Of the red, green and blue lasers employed in a color projection display, a laser configured to generate green light may pose more challenges since laser diodes that emit green light are not readily available. As such, in order to generate green light, an infrared (IR) diode laser, such as a laser diode, may be utilized in conjunction with a frequency doubler, such as a periodically poled lithium niobate (PPLN) crystal. The frequency doubler divides the wavelength of the IR signal in half so that an IR signal having a wavelength of 1060 nanometers can be frequency doubled to produce a green signal having a wavelength of 530 nanometers. This frequency doubling process, however, is a non-linear process having relatively low conversion efficiency, thereby adversely affecting the power consumption of the projection display. In this regard, an IR diode laser generally requires a substantial current to generate an output that may be utilized to create green light. As a result, the temperature of the IR laser may rise substantially which, in turn, may cause the wavelength of the signals generated by the IR laser to change. As the wavelength of the signals generated by the IR laser moves away from the wavelength that is required by the frequency doubling crystal to generate green light, the amount of green light generated by the frequency doubling crystal will be reduced. As such, the IR laser generally requires relatively rigorous control of its temperature, thereby increasing the cost and potentially decreasing the efficiency of the laser.
Additionally, displays, such as projection displays, are increasingly being employed in applications that require relatively small displays, such as cellular telephones, media players and the like. In some instances, however, projection displays that rely upon lasers for the generation of the signal are too large to satisfy the size requirement of these applications.
It would therefore be desirable to provide an improved projection display including, for example, a projection display that could be relatively small in order to be employed in a wider variety of applications.